1. Field of the Invention
This invention concerns a device for levelling a particulate material web, such as a wood-fibre mat laid out on a wire and intended for the production of wood-fibre boards, said material web being moved in relation to the device.
2. Description of Background Art
In the production of wood-fibre boards, glue-coated wood fibres are pneumatically conveyed from a container to a forming station. In this station, the wood fibres are laid out in the form of a mat on a wire, by means of which the fibres are conveyed to a pressing plant, where they are pressed into fibre boards under given pressure and temperature conditions. On its way to the pressing plant, the fibre mat passes a milling roller which is arranged transversely of the direction of conveyance and which mills the fibre mat to give it a smooth upper surface as well as a suitable thickness and a suitable weight before the pressing operation. The fibres removed from the fibre mat in the milling operation are recycled to the container, so as to subsequently be returned to the forming station and be laid out on the wire. The amount of wood fibres separated by the milling roller is fairly large and may, in some applications, be up to 25%. Since the amount of fibres separated and thus recirculated is fairly large, the fibres are worn and dehydrated to a disproportionate extent. Furthermore, the glue consumption and the power requirement of the fibre conveyance become excessive.